As shown in FIG. 1, a semiconductor light-emitting device made by mounting a semiconductor light-emitting element is composed of, for example, a semiconductor light-emitting element 1, a molded resin 2, a bonding wire 3, an encapsulant 4, and a lead frame 5. The structure comprising the electroconductive metal interconnects, e.g., the lead frame, and the insulating molded resin is referred to as the package.
Insulating materials provided by incorporating a white pigment in a thermoplastic resin, e.g., a polyamide, have already entered into general use as insulating materials used for molded resins (refer, for example, to Patent Document 1). In the case of semiconductor light-emitting devices where directionality is required of the emitted light, the light-emitting efficiency is required not just by the light emitted in the desired direction from the semiconductor light-emitting element, but also by causing light emitted in undesired directions to be reflected from, e.g., the molded resin, metal interconnects such as the lead frame, and reflectors, into the desired direction. Since thermoplastic resins such as polyamides are light permeable, the light-emitting efficiency of a semiconductor light-emitting device can be raised by incorporating—when light is to be reflected by the molded resin—a white pigment in the resin and reflecting the light emitted from the semiconductor light-emitting element by utilizing the difference in the refractive indices between the resin and white pigment.
Even when a white pigment is used in Patent Document 1, its reflection efficiency may not be satisfactory depending on the particular type of white pigment, and light absorbed in the molded resin and light penetrating through the molded resin also ultimately escape. Due to this, it has not been possible in some cases to concentrate the light from the semiconductor light-emitting element in the desired direction and the light-emitting efficiency of the semiconductor light-emitting device has been reduced as a result.
In addition, there is currently a trend toward higher reflow temperatures due to a strong trend toward the use of higher melting lead-free solders brought on by environmental concerns. Polyamides are thermoplastic resins, and polyamides are thus softened by this heat and the heat resistance of the package then becomes a problem in the case of packages that use polyamide. Furthermore, polyamides are subject to photodegradation and thermal degradation by ultraviolet radiation and heat, and degradation by light has become a problem in particular when light-emitting elements are used that have a light-emission range that extends into high-energy wavelength regions, such as the blue to near-ultraviolet semiconductor light-emitting elements whose commercialization has been ongoing in the recent years. Moreover, thermal degradation and photodegradation have become even more significant problems due to the heat and high luminous flux light generated by the semiconductor light-emitting element as a result of contemporary demands for brighter light-emitting elements.
Otherwise, an alumina-containing sintered ceramic may be used as the insulating material in those cases in which heat resistance is required (refer, for example, to Patent Document 2). A package that uses this ceramic does have a good heat resistance, but its production requires a high-temperature sintering step post-molding. This sintering step has posed the following problems: cost problems due, for example, to electricity costs; the ease of appearance of defective products due to changes in the size and shape of the molding caused by sintering; and an impaired productivity.
In contrast to the preceding, a case has also recently been introduced that is provided by molding a silicone resin composition that uses an organopolysiloxane for the resin and uses titanium oxide for the white pigment (refer, for example, to Patent Document 3). The use of the organopolysiloxane for the resin is intended to improve the heat resistance over that for the use of polyamide.
Patent Document 1: Japanese Patent Application Laid-open No. 2002-283498
Patent Document 2: Japanese Patent Application Laid-open No. 2004-288937
Patent Document 3: Japanese Patent Application Laid-open No. 2009-155415